Automatic guided vehicles are utilized in material handling systems to effectively and efficiently transport materials in a wide variety of industry environments such as factories and hospitals. Safety systems incorporated in the design of these vehicles include safety bumpers equipped with sensing and control devices to sense objects which come into contact with the bumper and stop the vehicle upon encountering an object in the vehicle path to prevent a collision of the vehicle with the object. Effective operation of these safety devices is essential to assure the safety of personnel and property in the vehicle's operational environment. These safety bumpers must be capable of resetting themselves and undergoing repeated operation without being damaged yet, the effectiveness of the bumper to stop the automatic guided vehicle upon contact with an object cannot be compromised. There should be no dead spots or zones in the bumper sensing field. The device should not cause nuisance shutdowns of the vehicle when personnel or property are not endangered.
Automatic guided vehicle safety bumpers of the prior art have included rigid or flexible bumper panels supported in front of the automatic guided vehicle by struts and stabilizing guy wires which allow displacement of the bumper panel by an object which comes into contact with it. Sensors are provided to detect movement of the bumper panel and send a signal to a control device which stops movement of the vehicle upon the occurrence of such a displacement.
Many safety bumpers of the prior art have utilized mechanical switches attached to the bumper struts and guy wires to send bumper panel displacement signals. Many of these devices lack the desired sensitivity necessary to stop movement of the vehicle upon contact with an object striking the panel at any possible location in the danger zone of travel. Other systems have offered greater sensitivity by utilizing sensors to detect displacement of a light beam reflected by a reflective panel on the inside of the central bumper panel to detect displacement of the panel, however, these systems may be excessively sensitive to movement of the bumper panel caused by irregularities in the surface over which the automatic guided vehicle is traveling causing unnecessary shutdown of the automatic guided vehicle material handling system.
Many safety bumpers of the prior art are difficult to adjust during manufacture and require expensive sensing components.